Wireless applications such as wireless personal area networks (WPANs), automotive radar, image sensing and others use millimeter-wave sources (i.e., sources operating at frequencies between 30-300 GHz). These millimeter-wave sources can be implemented either using fundamental oscillators or frequency doublers cascaded with lower frequency oscillators.
In millimeter-wave applications it is difficult to attain a high quality (i.e., low-phase noise) reference signal over a wide frequency range. With reference to frequency doubler architectures, wideband frequency doublers are preferred. One such wideband frequency doubler configured for wideband operation is the distributed frequency doubler. With the use of a differential input scheme, better fundamental rejection can be achieved. Distributed frequency doubler designs utilizing high-pass drain lines have been proposed to provide even better fundamental rejection. However, improvements in the performance of such devices are still needed.